Polymath Radar_layer

The radar_layer package is a costmap plugin for Nav2 Costmap 2d to turn radar tracks into data that can be used in a costmap. It is expected the radar track includes the object’s centroid position, velocity, position covariance, velocity covariance, and planar size of the detected object. This package allows the cost to be placed into the costmap in two different ways:

Footprint Stamping

This is the simplest method where a rectangle determined by the x and y size of the obstacle, is placed into the costmap as a lethal obstacle, around the obstacle’s centroid. This placed lethal obstacle can then be inflated with the inflation layer for planning purposes

2D Gaussian Process

The cost is distributed as a 2D gaussian, where the centroid position is the highest cost and the cost surrounding the centroid decreases like a 2D normal distribution, based on the position covariance. To incorporate the size of the obstacle, the position covariance is extended when evaluating the probability density function as follows:

with probability density function

where $\alpha$ is some covariance scaling factor for tuning, $\sigma_x$ and $\sigma_y$ are the position covariances of x and y, respectively, $l$ and $w$ are the length and width of the obstacle respectively, and $\mu_x$ and $\mu_y$ are the means of x and y respectively. Should the radar track also have velocity, the user may choose to project the gaussian distributed costmap into the future in order to plan to avoid a moving object in the future. The original Gaussian’s mean is projected forward with the velocity, and the projected covariance is spread and scaled down as a function of the velocity covariance.

The algorithm used in this package is based on the following work:

• H. Guo, Z. Huang, Q. Ho, M. Ang, D. Rus Autonomous Navigation in Dynamic Environments with Multi-Modal Perception Uncertainties. IEEE International Conference on Robotics and Automation, 2021.

@article{guo2023autonomous,
      title={Autonomous Navigation in Dynamic Environments with Multi-Modal Perception Uncertainties}, 
      author={Hongliang Guo and Zefan Huang and Qiheng Ho and Marcelo Ang and Daniela Rus},
      year={2021},
      journal = {IEEE International Conference on Robotics and Automation}
}

Topics

This costmap layer expects the radar tracks to be published in the ObstacleArray format defined by the navigation2_dynamic package

Configuration

Example fully-described XML with default parameter values:

``` costmap: costmap: ros__parameters: footprint: “[[-1.0,-0.3],[-1.0,0.3],[3.5,0.3],[3.5,-0.3]]” footprint_padding: 0.0 transform_tolerance: 2.0

  update_frequency: 20.0
  publish_frequency: 10.0

  global_frame: odom
  robot_base_frame: base_link

  width: 100
  height: 100
  origin_x: -50.0
  origin_y: -50.0
  resolution: 0.2
  rolling_window: true

  track_unknown_space: false
  unknown_cost_value: 25
  use_maximum: true

  plugins: ["radar_layer"]

  radar_layer:
    plugin: "radar_layer/RadarLayer"
    enabled: True
    number_of_time_steps: 10
    sample_time: 0.1
    minimum_probability: 0.15

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